6 week old Cornish X filled with fluid

I went out first thing this morning to feed our Cornish Xs and move their shelter around and found one dead, feet up. Looks like a heart attack. I was pretty peeved about this since the birds are 6 weeks old and we have quite a bit invested at this point. We had one that's been pretty lethargic the past few days and I wondered if I was looking at it, but as I walked around the shelter, I found her, sitting still, but alive, away from all the other birds. I picked her up and she didn't move, speak or put up a fuss. I tried to get her to stand and she just laid down and closed her eyes. I decided to process her before I lost her too.

When we eviscerated her, she was filled with about 4 cups of bright yellow, foul smelling liquid. She had very little meat on her, only about 1.5 lbs. For 6 weeks old, that isn't much at all. My guess is that her kidneys failed. We disposed of the entire bird.

Does anyone have any guess as to what condition she had and was the meat safe or was it the safest bet to dispose of it?